1. Field of the Invention
The invention relates to an electric shaver including a housing in which an electric drive is arranged for the oscillating movement of cutting knives of a shearing head, wherein the shearing head is provided with at least two cooperating cutting elements driven so as to be relatively displaceable.
2. Prior Art
A dry shaver of the initially defined kind is known, for instance, from U.S. Pat. No. 2,339,677. In that configuration the cutter head, which is comprised of a cutter head base, an upper shear element and a lower shear element, is arranged on an upper housing surface of a housing so as to be reciprocally movable transverse to the direction of movement of a lower shear element driven to oscillate in the longitudinal direction. Driving is effected via a double eccentric. Another known configuration may be taken from DE-U 17 11 665. The driving element of the electric drive in that case is coupled to both the lower knife and the shearing head provided with an upper knife, via a transmission element such as, e.g., a toothed gearing or a double eccentric or a double lever, in order to set the lower knife and also the complete shearing head in motion. In the main, such a configuration requires a high-performance electromotor, which causes a higher storage capacity and, consequently, a smaller number of shavings per storage cell charge to be observed. From DE-A1 36 31 120 it is known to set reciprocally driven masses such as, for instance, eccentrics and coupling elements as well as lower knives into a dynamic equilibrium by means of eccentric pendulums in order suppress undesired oscillations. Also a configuration of that type calls for an increased power output of the electric drive. Finally, DE 197 36 776 C2 discloses a configuration in which the drive motor is elastically mounted and connected with a shearing-knife-carrying shearing head part via coupling rods. With such a configuration, the vibration of the motor is directly diverted to the drive of the shearing blade in addition to the oscillating shearing knife drive derived from the motor itself.
The drive of a shearing blade in the known configurations, thus, is effected relative to the oscillating knives either in the direction of the oscillation movement or substantially normal to said oscillation, which only insignificantly influences the cutting performance and the reliable seizure of hardly seizable hairs of a beard.
The invention aims to provide a device of the initially defined kind, which, in addition to increasing the cutting performance and reducing the sliding resistance of the shearing blade on the skin, also is to further enhance the reliable seizure of hardly seizable hairs of a beard. To solve this object, the configuration according to the invention essentially consists in that a shearing head part carrying at least one shearing blade is hinged to be pivotal about at least one axis differing from the direction of the oscillating movement of the cutting knives and extending in the direction of the longer axis of the housing, and is driven to perform a pivotal movement about said axis. Due to the fact that the additional movement of the shearing blade relative to the oscillating cutting knives occurs neither in the direction of the oscillating movement nor in a direction transverse thereto, but in a pivotal movement about a central axis, not only a considerable reduction of the sliding resistance is observed, but also the effect that, on account of the slanted position relative to the direction of movement of the shearing blade, which is predetermined by the user, even hairs that can hardly be seized or are only difficult to seize by conventional shavers will be safely seized at the oscillating movement about the central axis. In addition to a markedly improved handling comfort, the cutting performance is improved, too. This effect may be enhanced in that the shearing head part carrying at least one shearing blade is hinged to be pivotal about two crossing axes differing from the directions of the oscillating movements of the cutting knives.
Advantageously, the configuration according to the invention is devised such that the mounting of the shearing head part carrying the shearing blade is designed as a cardanic mounting, preferably a spherical head mounting. Such a spherical head mounting, in the main, provides a substantially better adaptation of the shearing blade to irregular skin contours and hence an enhanced cutting performance, which is assisted even further by the oscillating pivotal movement.
In a particularly simple manner, the pivotal drive of the shearing head part carrying the shearing blade may be derived from at least one oscillating knife via tilting levers pivotally mounted on the shearing head or on the housing, whereby, in order to impart a suitable oscillating pivotal movement about the central axis, the configuration advantageously is devised such that two tilting levers are arranged, in particular on the oppositely located longitudinal inner walls of the shearing head, which tilting levers are each coupled with one of the relatively counterdriven cutting knives or cutting knife blocks. Besides the substantially linear operating direction usually predetermined by the user through the guidance of the shaver over the skin, a pivotal movement transverse to the direction of displacement, thus, occurs again and again simultaneously during the linear displacement, said oscillating pivotal movement transverse to the direction of displacement offering the opportunity to further reduce the application pressure while, nevertheless, reliably cutting irregularly projecting hairs of a beard. The coupling and dimensioning of the tilting levers enables a relatively large oscillation stroke of the cutting knives to be reduced to a small pivoting angle so as to avoid any remarkable additional load on the drive.
In a structurally particularly simple embodiment, the configuration may be devised such that the tilting lever(s) is/are hinged to be pivotal about the shearing head pivot axis extending transverse to the oscillation direction of the cutting knives. By pivoting the complete cutting head transverse to the oscillation direction on the housing itself, the adaptation of the position of the shearing blade relative to the skin is further enhanced with an irregular skin contour, said pivot axis, at the same time, being usable in a particularly simple manner for the pivotal movement oscillating on the gear by appropriate arrangement of the tilting levers.
Advantageously, the configuration is devised such that the shearing head part carrying the shearing blade is pivotally hinged to a shearing head part that is detachably connected with the housing. In this manner, the free or damped pivotability of the shearing blade about an axis extending transverse to the oscillating pivotal movement will be ensured and the removal of the entire shearing head, for instance, for cleaning purposes will be facilitated. In a particularly simple manner, the configuration is devised such that the pivot axis extending in the direction of the longer axis of the housing is arranged to be offset eccentrically near a longitudinal inner wall, thus reducing the zone in which the perforations of the shearing head foil are imparted only a slight pivotal dislocation with the axis arranged centrally.